1. Field of the Invention:
This invention relates to the art of taking x-ray pictures of a common object along two sight lines and, more particularly, to means for preventing cross-fogging of the x-ray pictures in such an arrangement.
2. Prior Art:
In a radiographic practice known as angiography, a radiopaque or contrast material is injected into the blood or lymphatic vessels of a patient and its progress through these vessels is observed by taking a series of x-ray pictures. The contrast materials currently used are toxic and, therefore, the amount injected into the patient must be limited. However, often it is necessary in this practice to obtain x-ray pictures in multiple projections, such as the front and side and so forth. In order to accommodate this requirement while minimizing both time of examination and the amount of contrast material used, pairs of x-ray tubes and film changers at right angles to each other have been used simultaneously, thus obtaining two orthogonal projections for each injection of contrast material.
It is well known that x-rays interact with the matter being x-rayed to produce scattering. This phenomenon, known as the Compton effect, produces noise on the x-ray film. While means have been devised to diminish the effect of scattered radiation on the primary film, namely the Potter-Bucky grid which is placed between the object being x-rayed and the film to absorb radiation which is not parallel to the line of sight of the picture, no attention has been focused on diminution of noise caused by scattered radiation from the second axis in a two axis angiogram.
It is a primary object of this invention to provide means to eliminate cross-fogging between the two axes of a two axis angiogram.
It is another object of this invention to eliminate such cross-fogging by means which are simple, reliable and inexpensive.